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After commita983b5ebee("mm: memcontrol: fix excessive complexity in memory.stat reporting"), we observed slowly upward creeping NR_WRITEBACK counts over the course of several days, both the per-memcg stats as well as the system counter in e.g. /proc/meminfo. The conversion from full per-cpu stat counts to per-cpu cached atomic stat counts introduced an irq-unsafe RMW operation into the updates. Most stat updates come from process context, but one notable exception is the NR_WRITEBACK counter. While writebacks are issued from process context, they are retired from (soft)irq context. When writeback completions interrupt the RMW counter updates of new writebacks being issued, the decs from the completions are lost. Since the global updates are routed through the joint lruvec API, both the memcg counters as well as the system counters are affected. This patch makes the joint stat and event API irq safe. Link: http://lkml.kernel.org/r/20180203082353.17284-1-hannes@cmpxchg.org Fixes:a983b5ebee("mm: memcontrol: fix excessive complexity in memory.stat reporting") Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Debugged-by: Tejun Heo <tj@kernel.org> Reviewed-by: Rik van Riel <riel@surriel.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.